Cochlear Implants Having MRI-Compatible Magnet Assemblies with Damping Liquid and Associated Methods

The present disclosure relates generally to the implantable portion of implantable cochlear stimulation (or “ICS”) systems.

ICS systems are used to help the profoundly deaf perceive a sensation of sound by directly exciting the intact auditory nerve with controlled impulses of electrical current. Ambient sound pressure waves are picked up by an externally worn microphone and converted to electrical signals. The electrical signals, in turn, are processed by a sound processor, converted to a pulse sequence having varying pulse widths, rates and/or amplitudes, and transmitted to an implanted receiver circuit of the ICS system. The implanted receiver circuit is connected to an implantable electrode array that has been inserted into the cochlea of the inner ear, and electrical stimulation current is applied to varying electrode combinations to create a perception of sound. The electrode array may, alternatively, be directly inserted into the cochlear nerve without residing in the cochlea. A representative ICS system is disclosed in U.S. Pat. No. 5,824,022, which is entitled “Cochlear Stimulation System Employing Behind-The-Ear Sound processor With Remote Control” and incorporated herein by reference in its entirety. Examples of commercially available ICS sound processors include, but are not limited to, the Harmony™ BTE sound processor, the Naida™ CI Q Series sound processor and the Neptune™ body worn sound processor, which are available from Advanced Bionics.

As alluded to above, some ICS systems include an implantable cochlear stimulator (or “cochlear implant”), a sound processor unit (e.g., a body worn processor or behind-the-ear processor), and a microphone that is part of, or is in communication with, the sound processor unit. The cochlear implant communicates with the sound processor unit and, some ICS systems include a headpiece that is in communication with both the sound processor unit and the cochlear implant. The headpiece communicates with the cochlear implant by way of a transmitter (e.g., an antenna) on the headpiece and a receiver (e.g., an antenna) on the implant. Optimum communication is achieved when the transmitter and the receiver are aligned with one another. To that end, the headpiece and the cochlear implant may include respective positioning magnets that are attracted to one another, and that maintain the position of the headpiece transmitter over the implant receiver. The implant magnet may, for example, be located within a pocket in the cochlear implant housing. The skin and subcutaneous tissue that separates the headpiece magnet and implant magnet is sometimes referred to as the “skin flap,” which is frequently 3 mm to 11 mm thick.

The present inventors have determined that conventional cochlear implants are susceptible to improvement. For example, the magnets in some conventional cochlear implants are disk-shaped and have north and south magnetic dipoles that are aligned in the axial direction of the disk. Such magnets are not compatible with magnetic resonance imaging (“MRI”) systems, and may have to be surgically removed from the cochlear the implant prior to the MRI procedure and then surgically replaced thereafter. Other cochlear implants include with a diametrically magnetized disk-shaped magnet that is rotatable relative to the remainder of the implant about its central axis, and that has a N-S orientation which is perpendicular to the central axis. The present inventors have determined that diametrically magnetized disk-shaped magnets are less than optimal because a dominant magnetic field, such as the MRI magnetic field, that is misaligned by at least 30° or more from the N-S direction of the magnet may demagnetize the magnet or generate an amount of torque on the magnet that is sufficient to dislodge or reverse the magnet and/or dislocate the associated cochlear implant and/or cause excessive discomfort to the patient.

More recently, cochlear implants with MRI-compatible magnet assemblies have been introduced. The MRI-compatible magnet assemblies have a case defining a central axis, a frame within the case that is rotatable relative to the case about the central axis, and a plurality of elongate diametrically magnetized magnets, i.e., diametrically magnetized magnets with respective lengths that are greater than the respective diameters, that are located in the frame and rotatable about their respective longitudinal axis relative to the frame. This combination allows the magnets to align with three-dimensional (3D) MRI magnetic fields, regardless of field direction, which results in very low amounts of torque on the magnets. The case is hermetically sealed by welding (e.g., laser welding) the case cover to the case base around the perimeter of the case after the frame and magnets are positioned therein. Examples of MRI-compatible magnet assemblies may be found in U.S. Pat. Nos. 9,919,154, 10,463,849, and 10,532,209. Another proposed magnet assembly, which includes a single elongate magnet, is described in PCT Pat. Pub. No. 2020/092185 A1.

Although such MRI-compatible magnet assemblies have proven to be a significant advance in the art, the present inventors have determined that they are susceptible to improvement. For example, a relatively small number of recipients of cochlear implants with MRI-compatible magnet assemblies have reported that they hear sound, which may be characterized as a “rattle,” when the associated headpiece is attached or removed. For example, some single-sided recipients wear a hearing aid on the contra-lateral side and the hearing aid may amplify sounds emanating from the MRI-compatible magnet assembly. One proposed solution involves hermetically sealing a liquid (e.g., a biocompatible oil) inside the magnet case that acts as a physical dampening medium between the moving internal components of the MRI-compatible magnet assembly. During assembly, the liquid is added to the case base along with the frame and magnets, the case cover is positioned on top of the case base, and the case cover is welded to the case base around the perimeter of the case to hermetically seal the case. The present inventors have determined that hermetically sealing a liquid inside the magnet case in this manner is susceptible to improvement. In particular, adding a volume of liquid sufficient to perform the damping function results in the surface of the liquid being adjacent to the case base and cover intersection where the weld is formed. The high temperature associated with welding (approx. 1700° C.) boils the liquid adjacent to the area being welded and adversely effects the weld.

A method of assembling a magnet assembly in accordance with one of the present inventions may include the steps of positioning a plurality of elongate diametrically magnetized magnets within a first case member including a first end wall and a first side wall portion, securing a second case member, including a second end wall and a second side wall portion, to the first case member to form a case, defining a central axis and in which the elongate diametrically magnetized magnets are located, by welding the first side wall portion to the second side wall portion, wherein one of the first and second end walls includes a port, introducing damping liquid into the case by way of the port, sealing the port after the damping liquid into the case has been introduced into the case by way of the port.

A magnet assembly in accordance with one of the present inventions may include a case defining a central axis, a plurality of elongate diametrically magnetized magnets within the case, the magnets defining a longitudinal axis and a N-S direction and being rotatable about the longitudinal axis relative to the case, and a damping liquid dispenser, including a reservoir with a port, damping liquid within the reservoir and a plug that seals the port, located within the case.

A method of assembling a magnet assembly in accordance with one of the present inventions may include positioning a plurality of elongate diametrically magnetized magnets and a damping liquid dispenser within a first case member including a first end wall and a first side wall portion, securing a second case member, including a second end wall and a second side wall portion, to the first case member to form a case in which the elongate diametrically magnetized magnets and damping liquid dispenser are located, and releasing damping liquid from the damping liquid dispenser after the case has been formed.

A cochlear implant in accordance with one of the present inventions may include a cochlear lead, an antenna, a stimulation processor, and such a magnet assembly or a magnet assembly produced by such methods.

The above described and many other features of the present inventions will become apparent as the inventions become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.

The following is a detailed description of the best presently known modes of carrying out the inventions. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the inventions.

1 7 FIGS.- 5 7 FIGS.- 11 FIG. 27 FIG. 11 28 FIGS.and 100 102 104 106 108 110 112 112 112 114 116 116 102 118 118 120 102 100 50 200 100 400 As illustrated for example in, an exemplary magnet assemblyincludes a case, with baseand a cover, a frame, a magnet subassemblywithin the frame that includes a plurality of elongate diametrically magnetized magnets′ and″ (collectively “magnets”) that define a N-S direction and are located within a holder, and damping liquid. The damping liquidmay be introduced into the caseby way of a port, and the portmay be thereafter sealed with a plugthat is welded to the case, as is discussed in greater detail below with reference to. The magnet assemblymay, in some instances, be employed a system() that includes a cochlear implant(described below with reference to) with the magnet assemblyand an external device such as a headpiece(described below with reference to).

102 1 108 108 102 1 110 108 1 1 112 114 102 108 2 2 112 2 112 114 112 The exemplary caseis disk-shaped and defines a central axis A, which is also the central axis of the frame. The frameis rotatable relative to the caseabout the central axis Aover 360°. The magnet subassemblyrotates with the frameabout the central axis A, and does not rotate relative to the frame about the central axis A. Each magnetis also rotatable within the holderrelative to the holder, the caseand the frameabout its own longitudinal axis A(also referred to as “axis A”) over 360°. The N-S direction of each magnetis perpendicular to the longitudinal axis Aabout which the magnetrotates. The holderholds all of the magnetsand fixes their positions relative to one another.

2 1 1 In the illustrated implementation, the longitudinal axes Aare parallel to one another and are perpendicular to the central axis A. In other implementations, the magnets within a magnet assembly may be oriented such that the longitudinal axes thereof are at least substantially perpendicular to the central axis A. As used herein, an axis that is “at least substantially perpendicular to the central axis” includes axes that are perpendicular to the central axis as well as axes that are slightly non-perpendicular to the central axis (i.e., axes that are offset from perpendicular by up to 5 degrees).

112 2 112 112 1 3 5 7 FIGS.and- Given the ability of each magnetto rotate about its longitudinal axis A, the magnetsalign with one another in the N-S direction in the absence of an external magnetic field that is strong enough to rotate the magnets out of alignment (e.g., an MRI magnetic field or a headpiece magnetic field). The at rest N-S orientation of the magnetswill be perpendicular to the central axis Ain the illustrated embodiment, as is illustrated in.

102 102 104 106 106 104 122 102 124 126 128 130 132 124 126 128 102 118 124 126 124 118 1 124 118 5 7 FIGS.- The caseis not limited to any particular configuration, size or shape. Referring more specifically to, the exemplary casein the illustrated implementation is, as noted above, a two-part structure that includes the baseand the coverwhich are secured to one another in such a manner that a hermetic seal is formed between the cover and the base. Suitable techniques for securing the coverto the baseinclude, for example, seam welding with a laser welder that creates a weld. The completed casehas end wallsand, a side wall, and first and second curved wallsandthat respectively connect the first and second end walls to the side wall. The end wallsandare planar, while the side wallis annular in shape and defines the outer perimeter of the case. The portmay extend through either one of the end wallsandand, in the illustrated implementation, extends through end wall. The portis located on the case central axis A, which is at the center of the end wall. The diameter of the portmay range from, for example, about 0.2 mm to about 1.0 mm. As used herein in the context of dimensions, the word “about” means +/−10%.

120 120 134 136 134 136 1 136 102 136 118 The plugis not limited to any particular configuration, size or shape. In the illustrated implementation, the plugincludes a stopperand a flangethat extends outwardly from the stopper. Although the stopperand flangeare circular in cross-sections perpendicular to the case central axis A, other shapes may be employed. The outer perimeter of the flange, i.e., the diameter in the illustrated embodiment, is also significantly smaller than that of the case. For example, the diameter of the flangemay range from about 0.3 mm to about 1.5 mm. Alternatively, in those instances where the portis relatively small (e.g., less than 0.3 mm), the port may be sealed by heating the area with a laser spot welder to cause the metal in that portion of the case to liquify and then seal the port when it cools.

100 108 110 104 106 104 106 122 102 116 102 118 120 118 134 118 136 124 120 102 138 136 100 1 2 3 4 100 108 102 112 102 108 114 5 FIG. 6 FIG. 7 FIG. 8 FIG. During manufacture of the exemplary magnet assembly, the frameand magnet subassemblymay be placed into the case base, and the case covermay then be positioned on the case base. The case base and coverandmay then be secured to one another by a welding process (e.g., laser welding), which results in the weldthat hermetically seals the case base and cover to one another to complete the case, as shown in. The damping liquidis thereafter introduced into the casethrough the portand allowed to settle under gravity at the bottom of the case, as shown in. The exemplary plugmay then be used to hermetically seal the port. In particular, the stoppermay be inserted into the portuntil flangerests on the case end wall. The plugmay be secured to the caseby a welding process (e.g., laser welding) which results in a weldthat extends around the perimeter of the flange, thereby completing the magnet assembly, as shown in. In summary, and turning to, in one exemplary method, the internal components of a magnet assembly may be placed into a first portion of a case (Step S), a second portion of the case may then be welded to the first portion to complete the case (Step S), damping liquid may then be introduced into the case through a port in a case end wall (Step S) and, after the damping liquid has settled under gravity at the bottom of the case, the port may then be sealed with a plug that is welded to the case end wall (Step S). Subsequent movement of the internal components of the magnet assembly, i.e., rotation of the framerelative to the caseand/or rotation of the magnetsrelative the case, the frameand the holder, will cause the damping liquid to encapsulate the internal components and thereby act as a physical dampening medium between the components.

7 FIG. 1 122 116 122 116 102 122 116 122 102 118 138 120 124 2 138 116 1 2 102 116 138 116 138 136 112 102 There are a number of advantages associated with the above-described method of assembling a magnet assembly. By way of example, and referring to, there is a relatively small distance Dbetween the location of the weldand the surface of the damping liquid. Formation of the weldafter the damping liquidhas been introduced into the casein accordance with conventional methods will, as noted above, cause the damping liquid to boil in the area adjacent to the area being welded which, in turn, adversely effects the weld. The present method, on the other hand, involves the formation of the weldprior to the introduction of the damping liquid, thereby obviating the issues associated with the boiling of damping fluid during the formation of the weld. Turning to weld that is formed after the damping fluid has been introduced into the caseby way of the port, i.e., the weldthat secures the plugto the case end wall, there is a relatively large distance Dbetween the location of the weldand the surface of the damping liquid. For example, in some instances, the distance Dmay be about 0.5 mm while the distance Dmay be about 2.3 mm. As a result, the formation of the weld that hermetically seals the casewith the damping liquidtherein, i.e., weld, is far less likely to cause the damping liquidto boil. The likelihood of damping liquid boiling is further reduced by the relatively small size of the weld, which extends around the perimeter of the plug flange, as compared to the weld, which extends around the perimeter of the case.

102 102 102 120 102 a With respect to materials, the case, the case(discussed below) may be formed from biocompatible paramagnetic metals, such as titanium or titanium alloys, and/or biocompatible non-magnetic plastics such as polyether ether ketone (PEEK), low-density polyethylene (LDPE), high-density polyethylene (HDPE), ultra-high-molecular-weight polyethylene (UHMWPE), polytetrafluoroethylene (PTFE) and polyamide. In particular, exemplary metals include commercially pure titanium (e.g., Grade 2) and the titanium alloy Ti—6Al—4V (Grade 5), while exemplary metal thicknesses for the casemay range from 0.20 mm to 0.25 mm. The plugmay be formed from the same material as the case.

102 102 100 102 102 102 102 102 a a a With respect to size and shape, the exemplary case(and) may have an overall size and shape similar to that of conventional cochlear implant magnets so that the magnet assemblycan be substituted for a conventional magnet in an otherwise conventional cochlear implant. The case(and) may also have an overall size and shape that is larger than that of conventional cochlear implant magnets in other embodiments. In some implementations, and depending on the number of magnets within the case(and), the diameter that may range from 9 mm to 17.40 mm and the thickness may range from 1.5 mm to 3.10 mm. The diameter of the caseis 15.2 mm, and the thickness is 3.10 mm, in the illustrated embodiment.

2 4 FIGS.- 4 FIG. 1 7 FIGS.- 4 FIG. 108 140 142 144 142 110 112 114 108 108 102 110 142 3 112 144 112 100 112 112 102 112 2 112 a Referring to, the exemplary frameincludes a diskand a magnet receptaclethat extends completely through the disk and is defined by inner walls. The magnet receptacleis configured to hold the magnet subassembly, including all of the magnetsand the holder, and has a relatively long portion and two relatively short portions. Suitable materials for the frame(as well as the framediscussed below), which may be formed by machining, metal injection molding or injection molding, include paramagnetic metals, polymers and plastics such as those discussed above in the context of the case. Referring more specifically to, there may be a relatively tight fit between the between the magnet subassemblyand the magnet receptacle. For example, the distance Dbetween the longitudinal ends of the magnetsand the inner wallsmay be about 0.08 to 0.15 in some implementations. Although the present inventions are not limited to any particular number, there are five elongate diametrically magnetized magnetsin the exemplary magnet assemblyillustrated in. Three magnets′ are relatively long, as compared to the other magnets, and two magnets″ are relatively short, as compared to the other magnets, in order to efficiently utilize the available volume within the case, as is best shown in. The exemplary magnets, which are otherwise identical, are circular in a cross-section that is perpendicular to the longitudinal axis Aand, in some instances, may have rounded corners. Suitable materials for the magnetsinclude, but are not limited to, neodymium-boron-iron and samarium-cobalt.

9 10 FIGS.and 114 146 146 146 148 112 146 2 112 146 112 146 146 114 146 150 146 114 Turning to, the exemplary holderincludes a plurality of tubes′ and″ (collectively “tubes”), with respective lumens, for the plurality of magnets. The tubesdefine the same longitudinal axes Aas the magnets. The number of tubescorresponds to the number of magnetsand, in the illustrated embodiment, there are three otherwise identical tubes′ that are relatively long and two otherwise identical tubes″ that are relatively short. The exemplary holderis an integral structure wherein the tubesare each attached to an adjacent tube (or tubes). As used herein, an “integral structure” is a structure where adjacent components (i.e., tubes) are attached to one another, remain attached to one another under normal use conditions, and cannot be separated from one another without destruction of the holder. Jointsmaintain the integrity of the connection between the tubes, and prevent ovaling of the tubes. In some instances, the tubesmay share a common wall portion, thereby reducing the overall width of the holder.

112 148 114 112 2 146 114 114 146 146 148 112 114 112 146 116 100 2 4 FIGS.- The magnetsare located within the lumensof the exemplary holderin the manner illustrated inand each magnetrotates about its longitudinal axis Arelative to the associated tube. To facilitate such rotation, the holdermay be formed from low friction material including, but not limited to, polymers, such as silicone, PEEK and other plastics, PTFE, and PEEK-PTFE blends, and paramagnet metals. In the illustrated implementation, the holderis a multi-lumen PEEK extrusion where all of the tubes are initially cut to the length of the relatively long tubes′, and the relatively short tubes″ are thereafter cut to their length. The diameter of the lumensmay be slightly larger (e.g., about 0.05 mm to about 0.2 mm larger) than the outer diameter of the magnetsto facilitate placement of the magnets into the holder, rotation of the magnetsrelative to the tubes, and the ingress of damping liquidinto the space between the tubes and the magnets as the damping liquid encapsulates the internal components of the magnet assembly.

9 FIG. 5 FIG. 114 2 112 2 112 114 2 112 102 114 102 114 102 100 Referring more specifically to, it should also be noted that exemplary holderhas a pre-set arcuate shape. The longitudinal axis Aof the center tubelies in a horizontal plane HP and the longitudinal axes Aof the remaining tubesare not located in the horizontal plane HP when the holderis in a relaxed (i.e., unstressed) state. The axes Adefine a curve C and, as a result, fewer than all of the tubesare in contact with the inner surface of the casewhen the holder is in a relaxed state. Referring to, there are only three lines of contact LC between the holderdue to the curvature and the inner surface of the caseas opposed to the minimum of five lines of contact which would be the case if the holder was not arcuate. The reduction in contact results in a corresponding result in friction between the holderand the inner surface of the case, as compared to an otherwise identical magnet assemblywithout an arcuate holder.

102 108 104 106 108 152 102 152 102 108 114 112 102 112 7 FIG. Friction may be further reduced by coating the inner surfaces of the caseand/or the surfaces of the framewith a lubricious layer. The lubricious layer may be in the form of a specific finish of the surface that reduces friction, as compared to an unfinished surface, or may be a coating of a lubricious material such as diamond-like carbon (DLC), titanium nitride (TiN), PTFE, polyethylene glycol (PEG), Parylene, fluorinated ethylene propylene (FEP) and electroless nickel sold under the tradenames Nedox® and Nedox PF™. The DLC coating, for example, may be only 0.5 to 5 microns thick. In those instances where the baseand a coverare formed by stamping, the finishing process may occur prior to stamping. In the illustrated implementation, the surfaces of the framemay be coated with a lubricious layer(e.g., DLC), while the inner surfaces of the casedo not include a lubricious layer, as shown in. The lubricious layerreduces friction between the caseand frame, while the low friction holderreduces friction between adjacent magnetsas well as between the caseand the magnets.

116 112 116 116 3 3 3 3 With respect to the damping liquid, damping liquids may include, but are not limited to, liquids that are biocompatible and are at least somewhat chemically inert because the liquid will encapsulate the magnets. By way of example, but not limitation, the damping liquid may be mineral oil or white cosmetic oil. The damping liquid may have a viscosity that is greater than or equal to about 86 centipoise (cps) and is less than or equal to about 150,000 cps. The volume of damping liquidemployed will depend on the particulars of the case, frame and magnets. In the illustrated embodiment, the volume of damping liquidmay range from about 20 mmto about 70 mmin some implementations, may be less than 82 mmin some implementations, and is about 30 mmin the illustrated implementation.

5 7 FIGS.- 112 100 1 102 114 As shown in, absent an external magnetic field that is strong enough to rotate the magnetsout of alignment (e.g., an MRI magnetic field or a headpiece magnetic field), the magnets of the exemplary magnet assemblywill remain substantially aligned with one another in the N-S direction and the N-S orientation of each magnet will be perpendicular or close to perpendicular to the central axis Aof the case. The magnets are also arranged an arcuate group defined by the holderin the illustrated embodiment.

11 FIG. 27 FIG. 28 FIG. 4 FIG. 5 7 FIGS.- 11 FIG. 100 200 202 400 50 400 402 410 1 112 2 114 108 1 112 1 Referring to, the exemplary magnet assemblymay part of a cochlear implantwith a housing(described below with reference to) that is employed in conjunction with an external device such as a headpiece(described below with reference to) in a system. The exemplary headpieceincludes, among other things, a housingand a magnetized disk-shaped positioning magnet. Here, the strength of the dominant headpiece magnetic field Bcauses the magnetsto rotate slightly about axis A() from the at rest orientations illustrated into the orientations illustrated in. The magnet holderwill, as a result of its preset shape, remain unstressed. The framewill also rotate about axis Aas necessary to align the magnetic fields of the magnetswith the N-S direction of the magnetic field B.

12 FIG. 4 FIG. 5 7 FIGS.- 2 112 2 112 2 108 1 112 2 100 2 112 2 1 102 Turning to, when exposed to a dominant MRI magnetic field B, the torque T on the magnetswill rotate the magnets about their axis A(), thereby aligning the magnetic fields of the magnetswith the MRI magnetic field B. The framewill also rotate about axis Aas necessary to align the magnetic fields of the magnetswith the MRI magnetic field B. When the magnet assemblyis removed from the MRI magnetic field B, the magnetic attraction between the magnetswill cause the magnets to rotate about axis Aback to the orientation illustrated in, where they are substantially aligned with one another in the N-S direction and the N-S orientation of the magnets is close to perpendicular to the central axis Aof the case.

1 12 FIGS.- 112 114 112 108 It should be noted the exemplary embodiments described above with reference tomay be modified in a variety of ways. By way of example, but not limitation, the number of magnetsmay be decreased to four or three or two or one, or may be increased to six or more. The holdermay be omitted and, in some instances, the magnetsmay be located within tubes that are formed from low friction material, as is discussed below. A two-piece frame, such that discussed below, may employed in place of the one-piece frame.

100 100 100 102 104 106 108 112 112 106 104 122 102 102 124 126 128 102 1 108 108 102 1 108 108 1 108 2 114 154 112 112 100 112 154 112 2 112 112 112 112 112 112 112 108 1 112 102 108 2 112 2 112 a a a a a a a a a a a a a a a a 13 16 22 FIGS.-and 22 FIG. 17 25 FIGS.- The exemplary magnet assemblyillustrated inis substantially similar to the magnet assemblyand similar elements are represented by similar reference numerals. To that end, the magnet assemblyincludes a case, with a baseand a cover, a frame, and elongate diametrically magnetized magnets′ and″. The coveris secured to the basewith a weld() that extends around the perimeter of the case, and the completed casehas end wallsand, a side wall. The caseis also disk-shaped and defines a central axis A, which is also the central axis of the frame. The frameis rotatable relative to the caseabout the central axis Aover 360°. Here, however, the frameincludes two separate frame membersand, the holderis omitted, and the magnet assembly includes damping liquid dispenser, which is discussed in greater detail below with reference to. With respect to the magnets, in addition to two of the above-described relatively long diametrically magnetized magnets′ and two of the above-described relatively short diametrically magnetized magnets″, the exemplary magnet assemblyincludes two dispenser magnets′″ that are part of the damping liquid dispenser. The dispenser magnets′″ are also each circular in a cross-section that is perpendicular to the longitudinal axis A, may have rounded corners, and may be formed from the same material as magnets′and″. The elongate diametrically magnetized magnets′,″ and′″ are referred to collectively “magnets”. The magnetsrotate with the frameabout the central axis A. Each magnetis rotatable relative to the caseand the frameabout its own longitudinal axis Aover 360°. The N-S direction of each magnetis perpendicular to the longitudinal axis Aabout which the magnetsrotate in the illustrated embodiment.

112 156 154 112 112 112 112 146 146 146 146 146 112 146 146 112 116 146 100 a a a a a a a a a a a. The dispenser magnets′″ are mounted on opposite ends of a reservoir(discussed below) and the length of the damping liquid dispenseris the same as that of the relatively long magnets′. The magnets′,″ and′″ may be located within tubes′,″ and′″ (collectively “tubes”) that are formed from low friction material. Suitable materials for the tubesinclude polymers, such as silicone, PEEK and other plastics, PTFE, and PEEK-PTFE blends, and paramagnet metals. The magnetsare free to rotate relative to the tubesin the illustrated embodiment. The inner diameter of the tubesmay be slightly larger (e.g., about 0.05 mm to about 0.2 mm larger) than the outer diameter of the magnetsto facilitate placement of the magnets into the tubes, rotation of the magnets relative to the tubes, and ingress of damping liquidinto the space between the tubesand the magnets as the damping liquid encapsulates the internal components of the magnet assembly

108 108 1 108 2 140 144 140 142 108 144 102 108 112 154 142 108 1 108 2 4 112 144 3 3 4 112 112 154 108 1 108 2 144 108 1 108 2 112 112 154 112 112 108 154 104 106 100 a a a a a a a a a a a a a a a a a a 14 16 FIGS.- Turning to the frame, each of the frame membersandincludes a partial diskwith inner wallsand has an overall C-shape with a curved end and two free ends. When the separate partial disksare positioned adjacent to one another in the manner illustrated in, the partial disks will together define a magnet receptaclethat extends completely through the frameand is defined by the inner walls. The case, the frameand the magnetsare respectively sized such that, when the magnets and the damping liquid dispenserare located within the magnet receptacle, the free ends of the frame membersandwill face one another and will be separated from one another by a distance D, while the longitudinal ends of the magnetswill be separated from the inner wallsby distance D. Distance Dmay be about 0.08 to 0.15 in some implementations and distance Dmay be about 0.2 to 0.6 in some implementations as noted above. The exemplary magnets′ and″ and damping liquid dispensermay be combined with the exemplary frame membersandby placing the magnets, dispenser and frame members on a surface, together with the frame members on opposite sides of the magnets and dispenser, and the frame member inner wallsfacing the longitudinal ends of the magnets and dispenser. The frame membersandmay then be pushed toward one another until the frame members abut the magnets′ and″ and damping liquid dispenser. The magnets′ and″, frameand damping liquid dispensermay then be transferred to the case base, and the case covermay thereafter be secured to the case base, by welding or other suitable technique, to complete the magnet assembly.

17 21 FIGS.- 20 FIG. 20 FIG. 154 156 112 156 158 160 162 164 116 160 162 166 116 164 162 112 156 156 168 2 170 112 172 174 170 174 158 168 112 156 112 112 Turning to, and as noted above, the exemplary damping liquid dispenserincludes a reservoiron which the dispenser magnets′″ are mounted. The exemplary reservoirincludes a generally cylindrical reservoir body, with an internal storage volume, and a portthat is temporarily sealed with a plug. Damping liquidis initially located within the storage volume. The portmay be located within a recessthat provides clearance to facilitate passage of the damping liquidwhen the plugis no longer sealing the port, as is discussed below. The magnets′″ may be connected to the reservoirthrough the use of any suitable instrumentality. In the illustrated implementation, the reservoirincludes a pair of annular flanges() that project outwardly in the direction of axis Aand define recesses, while the magnets′″ each include a cylindrical main portionand a disc-shaped projection. The lengths and diameters of the recessesare the same as those of disc-shaped projections, which facilitates the close fit illustrated in, and adhesive (not shown) may be used to secure the projections to the reservoir bodyand flanges. The magnets′″ also have the same N-S orientation relative to the reservoir, i.e. they are N-S aligned with one another and face in the same N-S direction, which allows the magnets to together function as a single elongate diametrically magnetized magnet in the manner described above with reference to magnets′ and″.

156 156 160 116 154 102 160 102 108 112 160 116 a a 3 3 3 3 The exemplary reservoirmay, for example, be formed from two molded reservoir halves (not shown) that are ultrasonically welded together. Suitable materials for the reservoirinclude, but are not limited to, PEEK and other engineering polymers. The internal storage volumemay be equal to the intended volume of damping liquidto be dispensed by the dispenserinto the interior of the case. As such, the size of the internal storage volumewill depend on the particulars of the case, frameand magnets. In the illustrated embodiment, the size of the internal storage volume(and volume of damping liquid) may range from about 7 mmto about 20 mmin some implementations, may be less than about 25 mmin some implementations, and is about 8.6 mmin the illustrated implementation.

164 162 116 160 100 164 162 164 164 112 164 122 a The exemplary plugis configured to seal the portand prevent the damping fluidfrom exiting the internal storage volumeuntil the plug is heated to at least a predetermined temperature which causes the plug to shrink or melt. The orientation and/or movement of the magnet assemblyduring and/or after heating will cause the shrunk or melted plugto fall out of, and thereby open, the port. For example, the port may be unsealed by heating the plugto at least the melting point of the material from which the plug is formed. In some instances, the plugmay be formed from wax or a wax-like material such as paraffin wax (melting temperature of 55° C. to 75° C.), bees wax (melting temperature of 62° C.), stearin wax (melting temperature of 54° C. to 74.5° C.) and polyethylene glycol (melting temperature of 51° C. to 53° C.). In some embodiments, the plug materials may have respective melting points that range from about 50° C. to about 80° C., which are temperatures associated with post assembly processes such as gross leak testing and ethylene oxide (“EtO”) sterilization. As used herein in the context of temperature, the word about means +/−5%. For example, the plug material may have a melting point of about 50° C. in some implementations. The melting temperature should also be less than the demagnetization temperature of the magnets, which may be about 80° C. to about 100° C. It should be noted that, due to the distance between the plugand the weld, the plug will typically not shrink or melt during the welding process and will remain intact until, for example, a post assembly process.

22 23 FIGS.and 22 23 FIGS.and 24 25 FIGS.and 26 FIG. 100 154 162 164 116 154 116 162 166 102 100 112 2 100 11 12 13 100 108 102 112 102 108 146 a a a a a a Turning to, which respectively show the exemplary magnet assemblyand damping liquid dispenserafter the porthas been unplugged by, for example, heating the plug, it should be noted that the damping liquidis gravity fed through the open port. Rotation of the damping liquid dispenserfrom the orientation illustrated into, for example, the orientation illustrated inwill result in the damping liquidflowing through the port, through the recessand into the interior of the case. Such rotation may be accomplished by simply reorienting the entire magnet assemblyby causing the magnetsto rotate about their axes Awith a magnetic field. Such rotation may occur as part of the manufacturing process and/or after the magnet assemblyhas been implanted with a cochlear implant. In summary, and referring to, in one exemplary method, the internal components of a magnet assembly, including the magnets and the damping liquid dispenser, may be placed into a case (Step S), the case base and cover may then be welded to one another (Step S), and damping liquid may be released from the damping liquid dispenser into the case by unplugging the damping liquid dispenser port (Step S). Subsequent movement of the internal components of the magnet assembly, i.e., rotation of the framerelative to the caseand/or rotation of the magnetsrelative the case, the frameand the tubes, will cause the damping liquid to encapsulate the internal components and act as a physical dampening medium between the components.

100 154 104 106 122 154 a There are a number of advantages associated with the magnet assemblyand associated methods. By way of example, but not limitation, the damping fluid remains within the damping fluid dispenserwhile case baseand coverare being welded to one another, thereby obviating the issues associated with boiling damping fluid during the formation of the weld. The use of the damping fluid dispenseralso facilitates the use of a conventional case.

13 26 FIGS.- 112 112 108 a. It should be noted the exemplary embodiments described above with reference tomay be modified in a variety of ways. By way of example, but not limitation, the number of magnets′ and″ may be decreased to three or two or one, or may be increased to five or more. A one-piece frame, such that discussed above, may employed in place of the two-piece frame

100 100 200 200 202 204 206 208 206 210 212 212 212 100 208 202 202 208 204 212 208 214 214 216 214 212 212 a a a a a a 27 FIG. One example of a cochlear implant (or “implantable cochlear stimulator”) including the present magnet assembly(or) is the cochlear implantillustrated in. The cochlear implantincludes a flexible housingformed from a silicone elastomer or other suitable material, a processor assembly, a cochlear lead, and an antennathat may be used to receive data and power by way of an external antenna that is associated with, for example, a sound processor unit. The cochlear leadmay include a flexible body, an electrode arrayat one end of the flexible body, and a plurality of wires (not shown) that extend through the flexible body from the electrodes(e.g., platinum electrodes) in the arrayto the other end of the flexible body. The magnet assemblyis located within a region encircled by the antenna(e.g., within an internal pocketdefined by the housing) and insures that an external antenna (discussed below) will be properly positioned relative to the antenna. The exemplary processor assembly, which is connected to the electrode arrayand antenna, includes a printed circuit boardwith a stimulation processorthat is located within a hermetically sealed case. The stimulation processorconverts the stimulation data into stimulation signals that stimulate the electrodesof the electrode array.

28 FIG. 60 200 300 400 Turning to, the exemplary cochlear implant systemincludes the cochlear implant, a sound processor, such as the illustrated body worn sound processoror a behind-the-ear sound processor, and a headpiece.

300 60 302 304 306 308 310 312 314 316 304 312 400 402 404 406 408 410 400 306 412 410 100 200 408 208 400 400 200 214 212 212 a a The exemplary body worn sound processorin the exemplary ICS systemincludes a housingin which and/or on which various components are supported. Such components may include, but are not limited to, sound processor circuitry, a headpiece port, an auxiliary device portfor an auxiliary device such as a mobile phone or a music player, a control panel, one or more microphones, and a power supply receptaclefor a removable battery or other removable power supply(e.g., rechargeable and disposable batteries or other electrochemical cells). The sound processor circuitryconverts electrical signals from the microphoneinto stimulation data. The exemplary headpieceincludes a housingand various components, e.g., a RF connector, a microphone, an antenna (or other transmitter)and a diametrically magnetized disk-shaped positioning magnet, that are carried by the housing. The headpiecemay be connected to the sound processor headpiece portby a cable. The positioning magnetis attracted to the magnet assemblyof the cochlear stimulator, thereby aligning the antennawith the antenna. The stimulation data and, in many instances power, is supplied to the headpiece. The headpiecetranscutaneously transmits the stimulation data, and in many instances power, to the cochlear implantby way of a wireless link between the antennae. The stimulation processorconverts the stimulation data into stimulation signals that stimulate the electrodesof the electrode array.

412 312 300 406 300 400 In at least some implementations, the cablewill be configured for forward telemetry and power signals at 49 MHz and back telemetry signals at 10.7 MHz. It should be noted that, in other implementations, communication between a sound processor and a headpiece and/or auxiliary device may be accomplished through wireless communication techniques. Additionally, given the presence of the microphone(s)on the sound processor, the microphonemay be also be omitted in some instances. The functionality of the sound processorand headpiecemay also be combined into a single head wearable sound processor. Examples of head wearable sound processors are illustrated and described in U.S. Pat. Nos. 8,811,643 and 8,983,102, which are incorporated herein by reference in their entirety.

Although the inventions disclosed herein have been described in terms of the preferred embodiments above, numerous modifications and/or additions to the above-described preferred embodiments would be readily apparent to one skilled in the art. The inventions include any combination of the elements from the various species and embodiments disclosed in the specification that are not already described. It is intended that the scope of the present inventions extend to all such modifications and/or additions and that the scope of the present inventions is limited solely by the claims set forth below.